Detection systems, in general, have an equalizer followed by a detector. The equalizer shapes input signal from an optical disk read mechanism to have particular characteristics and the detector processes the equalized signal to retrieve the information stored on the optical disk. Peak detectors, threshold based bit-by-bit detectors with and without simple post-processing for d=2 code constraint violation, and partial response Viterbi detectors are the proposed (or used) detection schemes for DVD channels. Peak detection systems (see prior arts and systems described in U.S. Pat. No. 5,680,380 M. Taguchi et. al, U.S. Pat. No. 6,028,833 Takeshi Maeda et. al, JP 10134489A2 Yokota Hachiro et. al), were perhaps, the first and the simplest detection systems used in optical playback. As the information storage density increases, the detection performance severely degrades due to inter-symbol interference. Threshold based bit-by-bit detectors having symmetrical equalized targets with and without simple post-processing schemes that possibly correct the d=2 code constraint violation (refer to Srini Gopalaswamy et. al “Simple detection technique for d=2 coded optical recording channels”, ICC'99 Proceedings, Vancouver, Canada, June 1999, T. Nakagawa et. al “A simple detection method for RLL codes (Run detector), “IEEE Tr. Magn., Vol. 33, No. 5, September 1997) have been proposed. Although these detectors are simple, their bit-error-rate performance is away from maximum achievable performance. Partial response equalizers followed by Viterbi detectors (refer to U.S. Pat. No. 5,680,380, Japan Patent JP101344892A2, and publications J. W. M. Bergmans et. al “Transition detector for CD and DVD,” IEEE Tr. Consumer Electronics, Vol. 46, No. 1, February 2000, pp.16–19, H. Hayashi et. al “Viterbi decoding circuit for DVD players,” Optical Data Storage'96, 1996, Chang Hun Lee et. al “A PRML detector for a DVDR system,” IEEE Tr. Consumer Electronics, Vol. 45, No. 2, May 1999) are the other class of detectors that use complex detection systems. These give poorer performance on shorter target responses due to noise enhancement and for longer target responses, the detectors are enormously complex. The first two preliminary post-processing blocks of the data processing apparatus of the present invention are similar to the scheme given in reference publications Srini Gopalaswamy et. al “Simple detection technique for d=2 coded optical recording channels”, ICC'99 Proceedings, Vancouver, Canada, June 1999 and T. Nakagawa et. al “A simple detection method for RLL codes (Run detector), “IEEE Tr. Magn., Vol. 33, No. 5, September 1997.